110 FOREST PLANTING. 



at. But no return of wood material is realized when 

 they have to be removed later on, while timber obtained 

 from the hardier protecting forest-trees pays at least the 

 expense of cutting, and, sometimes, even the cost of 

 planting. 



For nurses to the young, ^hade-enduring trees, such 

 kind of trees are usually selected as cause only a light 

 shade. So, for instance, the principal species of the firs, 

 as Abies pectinata, A. nobilis, and, upon good soil, the 

 spruce may be advantageously grown in the shade of the 

 common pi e or birch ; the beech, which is quite as diffi- 

 cult to grow as Abies pectinata or picea, can be grown in 

 the shade of the poplar, willow, alder, etc. If the nurses 

 are properly selected they will grow quickly without 

 preventing the development of the future stock of 

 trees, but their own value increases with the length of 

 time they remain. These nurses, belonging mostly to 

 the light-needing varieties, afford still another advantage 

 to the protected trees, as they have the tendency to 

 crowd out such trees of their own kind as grow up 

 too thickly, and to drop off, for want of light and air, 

 their own lower branches, furnishing thus to the pro- 

 tected shade-enduring trees every condition to mature 

 and attain a sound development. 

 2. Cleaning and Thinning. 



We are able to obtain great advantages both in natural 

 and artificial plantations by applying a proper system of 

 cleaning and thinning. 



Cleaning. As soon as the nurses threaten to over- 

 whelm with too much shade the protected young 

 trees, of which we have been speaking, they have to be 

 cut down so far as to prevent them from interfering 

 with the luxuriant growth of the future and predomi- 

 nant stock of trees. 



In the natural reproduction of forests, the quick grow- 

 ing sprouts from stumps become often very troublesome, 



